Question

我需要通过连接多个表在一个实体类中构建以下查询。

SELECT t1.column_id_1
  FROM table1 t1,
       Table2 t2,
       Table3 t3,
       Table4 t4,
       Table5 t5
WHERE     t1.COLUMN_ID_1 = t2. COLUMN _ID_1
       AND t2.COLUMN_ID_2 = t3. COLUMN_ID_2
       AND t3.COLUMN_ID_3 = t4. COLUMN_ID_3
       AND t4.COLUMN_ID_4 = t5. COLUMN_ID_4

请分享一些想法

Answer 1

这取决于您的模型如何映射到数据库。例如，如果T1映射到A类，T2映射到B类，并且A被声明为：

@Entity @Table(name = "t1")
public class A {
    @ManyToOne @JoinColumn(name = "COLUMN_ID_1")
    private B b;
}

@Entity @Table(name = "t2")
public class B {
    @Id @Column(name = "COLUMN_ID_1)
    private Integer id;
}

然后在JPQL中你只需编写

select b.id
from A a
join a.b as b

以及其他表格。

如何编写jpa查询来连接多个表

1 个答案: